The present invention relates generally to a multi-layer material, and more particularly to a multi-layer material including a regrind layer containing a dye that is selected so as to protect light-sensitive contents of the container from environmental light.
It is well-known that certain nutritional products are sensitive to light. For example, low acid liquid food products typically contain nutrients, including, but not limited to vitamins such as vitamin B2 (riboflavin), that are sensitive to light. Exposure of such food products to light can result in damage to the biological activity of these nutrients and/or to the taste or other characteristics of the products. This presents a particular challenge in the packaging of food products, including medical and pediatric nutritional products, because such products are subject to labeling requirements that require that the nutritional contents, e.g., vitamin contents, of the food product be specifically identified. In those cases in which the listed nutritional contents are light-sensitive, there may be a reduction in the amount or activity of one or more of the nutritional contents of the product over time due to light exposure, thereby causing the food product to be out of compliance with its labeling. In such a situation, it may be necessary to reduce the shelf-life of the food product, and thus increase the cost of the food product. Alternatively, it may be necessary to increase volume of the nutritional contents of the product, for example, by way of vitamin fortification, which also increases the cost of the food product. It is preferable that a light-protective package be provided so that the nutritional contents of the product remain within the ranges specified in the labeling, thereby providing a longer shelf-life for the product.
U.S. Pat. No. 5,750,226 to Macauley, et al. discloses a bottle designed to provide protection for light-sensitive products contained therein. U.S. Pat. No. 5,750,226 is incorporated herein by reference, in its entirety. Macauley, et al. disclose a bottle having a multi-layered wall structure. The wall includes inner and outer layers of food grade polypropylene, a regrind layer positioned between the inner and outer layers of food grade polypropylene, and a pair of high temperature adhesive layers. The wall further includes barrier layer. The adhesive layers serve to bond the other layers to the barrier layer. Titanium dioxide is incorporated into the food grade polypropylene layers and into the regrind layer in order to reduce light transmission through the wall. The titanium dioxide imparts a white color to each layer in which it is present.
Titanium dioxide is an inert material that can be used in both retort and aseptic packaging techniques. Titanium dioxide is a reflective material, i.e., it works by reflecting light away from the contents of the product. Although titanium dioxide effectively reflects light having a wavelength above approximately 500 nanometers, it has been found that some light having a wavelength below 500 nanometers is reflected when a bottle wall contains relatively high amounts of titanium dioxide. However, as discussed in U.S. Pat. No. 5,750,226, high concentrations of titanium dioxide can create significant problems in the manufacturing of containers. In addition, it can be difficult to achieve high titanium dioxide concentrations in relatively thin container walls.
Although the bottle disclosed by Macauley, et al. provides significantly enhanced light barrier characteristics over prior art bottles, it is desirable to provide new container that is constructed to provide enhanced light barrier characteristics, even when the container wall is relatively thin. In particular, it is desirable to provide a container that is constructed to reduce or eliminate the transmission of light having the wavelengths that will tend to degrade the nutritional contents of a food product contained by the container.